Field of the Invention
The invention is directed generally to polymer electrolytes for lithium batteries and, more specifically, to new polymer cathode binders that are stable to higher voltages than has been possible with conventional binders used in lithium polymer batteries.
The development of solid state polymer batteries has been dominated by ion-conducting polymer electrolytes made from poly(ethylene oxide) (PEO). Unfortunately, PEO suffers from at least two major drawbacks: 1) its ionic conductivity is highly temperature dependent and 2) its stability under highly oxidizing conditions is low. PEO crystallizes at 60° C., below which point its ionic conductivity is severely reduced. PEO is stable only to about 3.8 V vs Li+/Li, as higher voltages present oxidizing conditions that render it unstable. These two drawbacks limit the overall power and voltage at which batteries that use PEO electrolytes can operate and also limit the temperature range in which such batteries can operate.
It would be useful to find a solution that overcomes these drawbacks so that a Li polymer battery could operate stably at higher voltages without suffering from increased oxidization, thus improving long-term battery stability and increasing battery power.